An approach of reducing the background induced by neutrons

The background induced by interactions of neutrons with detector material (and shield material) is difficult to be rejected. It is one of the most important factors to affect the sensitivity of a balloon-borne gamma-ray astronomical telescope. The main component of neutron flux at the major detector of the telescope is incident neutrons, that consists of atmospheric neutrons and neutrons locally produced in the balloon platform. Therefore, shielding the detector from incident neutrons is a possible way to reduce the background. NaI (T1) crystal is very widely used in gamma-ray astronomical telescopes. Through balloon-borne experiment it is shown that up 6 LiF shield is effective to reduce the background in NaI crystal.